As explained above, air flowing through the PCV system passes from the air cleaner, through the inlet hose, into the engine valve cover and crankcase and then discharges through the PCV valve and outlet hose to the intake manifold. When an engine is operated under a heavily loaded condition for a relatively long period, an excess of crankcase air/vapors may be generated which exceeds the capacity of the PCV valve. When this happens, the excess volume of air/vapor may be discharged from the crankcase and through the normal intake hose into the air cleaner. In cold weather and under these conditions, this reverse flow of the air/vapor mixture could result in condensation of any water vapor where the air/vapor empties into the interior of the air cleaner assembly. To prevent accumulations of water in the air cleaner, a drain hole in its lower wall is provided to allow water to escape.
Under normal engine operating conditions, air flow to the PCV system may come from two sources. The primary source is air drawn from the engine air filter assembly and through its primary air filter. A secondary source of air is through the aforesaid drain hole. Since air which may mix with oil in the crankcase must be filtered to prevent contamination of engine oil, a secondary air filter is necessary for both of these sources.
Prior to the improved unitary filter assembly of this application, filters have been used to cover the outlet connection of the PCV system to the crankcase, one for each of the above identified sources. These filters naturally would absorb any water condensation. In cold weather and under certain operating conditions, this absorbed water can freeze. When this happens, the frozen water could block air flow of the PVC system.
In previous vehicles manufactured by the assignee of this application, the two secondary filters identified above are insertably supported in a recess-like filter housing or open ended subhousing of the air cleaner housing. This subhousing is conveniently formed in one corner of the air cleaner's interior. The drain hole is formed through the bottom wall of the air cleaner housing. The recess or sub-housing is formed with an opened upper end for insertion of the filters. In assembling the filters, a small spacer member is first inserted into the sub-housing. Next, a first filter is inserted and is positioned by the spacer over the drain hole. A second spacer member is then inserted. Finally, a second filter is inserted into a position spaced above the PCV's air outlet to the engine. The use of these many pieces is undesirable from a manufacturing and assembly viewpoint.
Functionally, the above described multi-piece filter arrangement is quite effective in filtering air and preventing freezing of the lower filter. After a period of use, the filters become dirty and should be replaced. With the above described multi-piece arrangement, replacement of the individual filters and insertion of spacer members is inconvenient and time consuming. Since the parts are disposed within the confines of the small housing, the assembly is also difficult. The lowest filter is particularly difficult to replace. Another concern is that the first spacer, first filter, second spacer and second filter may be reinstalled incorrectly into the housing or in an improper order. This is of concern since an engine which is operated without proper PCV air filtration can produce excessive emissions.